The present invention relates to a compression nail assembly for engagement with an element fixed to a bone, such as a cotter pin, for placing bone parts on either side of a fracture in compression, and specifically to an assembly of the above type which includes a tightening sleeve and a tightening mandrel configured for insertion into the sleeve and having an end portion shaped for engaging the element fixed to the bone.
With a compression nail assembly of the above conventional type, known as a Kaessmann-nail, it is possible to realize stress-stable osteosynthesis of fractures and pseudarthrosis on long tubular bones. Its use has been developed on the basis of the Kuntscher method, and in deviation from conventional marrow nail placement, is not based on the elastic tightening of the nail in an irregularly shaped marrow cavity. Rather, an optimum mechanical arrangement required for an undisturbed osteogenesis is achieved in the fracture gap with the Kaessmann compression nail placement, in that bone and metal implants, such as a tightening sleeve and a tightening mandrel, can be combined into a mutually clamped system by the use of measurable, interfragmentary pressure forces. Such a system remains essentially uninfluenced by external mechanical disturbance factors. The stability of a marrow nail osteosynthesis is thus increased many times.
In the known Kaessmann compression nail assembly, the tightening mandrel has an eyelet at one end. During implantation, it is necessary to pass an element, such as a cotter pin, through the bone and eyelet in order to secure the mandrel for subsequent tightening.
The manipulation required to implant this known compression nail is time consuming. The particular difficulty is to find the eyelet with the cotter pin as it is guided through the bone. The search for the eyelet with the cotter pin or with a drilling tool, respectively, is monitored through an image sensor. The instruments employed in the search for the eyelet interfere with the path of the X-rays of the image sensor and thus with the reproduction of the eyelet on the monitor screen of the image sensor.